Articulating rod assembly

ABSTRACT

An articulating assembly includes a first elongated element for attachment to a first anatomical region, and a second elongated element for attachment to a second anatomical region. In at least one embodiment, a coupling connects the first and second elongated elements. The coupling includes a moveable joint configured to allow polyaxial movement of the first elongated element with respect to the second elongated element. The assembly further includes a locking mechanism. The locking mechanism is operable in an unlocked condition to permit polyaxial movement of the first elongated element with respect to the second elongated element, and a locked condition to immobilize the movable joint and fix the position of the first elongated element with respect to the second elongated element.

RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 61/473,342, filed Apr. 8, 2011, the contents ofwhich are incorporated by reference herein in its entirety and for allpurposes.

TECHNICAL FIELD

The present disclosure relates generally to surgical assemblies, andparticularly to an articulating assembly that allows an elongated memberto be angularly adjusted in multiple planes. The articulating assemblymay be used, for example, to properly align fixation members with apatient's cervical vertebra and occipital region, or in a patient'slumbopelvic spine.

BACKGROUND

When performing posterior cervical stabilization, the surgeon typicallyplaces screws into the lateral mass of the cervical vertebral bodyfollowed by a titanium rod and set screws. This construct providesstabilization of the cervical spine to aid in fusion of one or morelevels. Occasionally, one end section of the rod is anchored to a plateattached to the occipital region in a procedure called occipitocervicalstabilization. In these constructs, the rod is characterized by twosections—a first section that extends over the cervical spine and asecond section that connects to the occipital plate at an angle relativeto the first section. One example of an occipitocervical fixationassembly 100 is shown in FIG. 1.

Fixation assembly 100 includes a pair of spinal rods 110. Each rod 110is inserted into a series of screw assemblies 120 configured foranchoring into a vertebral body. Each screw assembly 120 includes a bonescrew 130, a rod receiver 140, and a securing element 150 for lockingone of the rods 110 into the rod receiver. Each rod 110 includes a firstsection 110 a configured to extend over the cervical vertebrae and asecond section 110 b configured to attach to the patient's occipitalregion. The second sections 110 b are anchored to an occipital plate 160having two receivers 170 and two securing elements 180. Each rod 110 isbent to form an angle between its first section 110 a and second section110 b.

In conventional occipitocervical fixation assemblies, the rod may bebent prior to placement to form the angle between the first and secondsections. The pre-bent rod may be used to connect the screw or hookplaced at C2 with the occipital plate. Alternatively, the screw or hookmay be placed at C1 or C3. Because every patient has a differentanatomy, one rod configuration will not suit all patients. Among othervariables, the angle between the first and second rod sections will varyfrom patient to patient. Therefore, a pre-bent rod may not preciselymatch a patient's anatomy as the rod is placed. In many cases, thepre-bent rod requires further adjustment during placement, and must bebent intraoperatively.

Bending a rod prior to and during operation can be a time consuming andcumbersome process. In addition, bending the rod can create stress inthe rod that decreases fatigue strength of the rod material. If fatiguestrength is significantly reduced, the integrity of the rod can becompromised and pose a significant risk to the patient. The problemswith rod bending are experienced not only with occipitocervical fixationassemblies, but are also experienced with lumbopelvic spine fixationassemblies, and other implant systems featuring elongated elements thatmust be manually configured to conform to specific spatial requirements.

SUMMARY

The drawbacks of conventional implant systems, and the practice ofbending and shaping elongated elements, can be avoided with articulatingassemblies in accordance with the invention.

Articulating assemblies in accordance with the invention may include anadjustable articulating assembly for implantation in a human or animal.The assembly may include a first elongated element for attachment to afirst anatomical region, and a second elongated element for attachmentto a second anatomical region. A coupling may connect the first andsecond elongated elements. The coupling may include a moveable jointconfigured to allow polyaxial movement of the first elongated elementwith respect to the second elongated element. The assembly may furtherinclude a locking mechanism. The locking mechanism may be operable in anunlocked condition to permit polyaxial movement of the first elongatedelement with respect to the second elongated element, and a lockedcondition to immobilize the movable joint and fix the position of thefirst elongated element with respect to the second elongated element.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary and the following detailed description will bebetter understood in conjunction with the drawing figures, in which:

FIG. 1 is a perspective view of components of an occipitocervicalstabilization system;

FIG. 2 is a truncated perspective view of an articulating fixationassembly in accordance with one embodiment;

FIG. 3 is a truncated side view of components of the assembly in FIG. 2,shown in a first arrangement;

FIG. 4 is a truncated side view of components of the assembly in FIG. 2,shown in a second arrangement;

FIG. 5 is a truncated side view of components of the assembly in FIG. 2,shown in a third arrangement;

FIG. 6 is a truncated side view of components of the assembly in FIG. 2,shown in cross section in a fourth arrangement;

FIG. 7 is a truncated side view of components of the assembly in FIG. 2,shown in cross section in a fifth arrangement;

FIG. 8 is a truncated side view of components of the assembly in FIG. 2,shown in cross section in a sixth arrangement;

FIG. 9 is a truncated perspective view of components of the assembly inFIG. 2;

FIG. 10 is a truncated side view of components of the assembly in FIG.2;

FIG. 11 is a truncated perspective view of an articulating fixationassembly in accordance with another embodiment;

FIG. 12 is a truncated side view of components of the assembly in FIG.11, shown in a first arrangement;

FIG. 13 is a truncated side view of components of the assembly in FIG.11, shown in a second arrangement;

FIG. 14 is a truncated side view of components of the assembly in FIG.11, shown in a third arrangement;

FIG. 15 is a truncated side view of components of the assembly in FIG.11, shown in cross section in a first locked arrangement;

FIG. 16 is a truncated side view of components of the assembly in FIG.11, shown in cross section in a second locked arrangement;

FIG. 17 is a truncated side view of components of the assembly in FIG.11, shown in cross section in a third locked arrangement;

FIG. 18 is a side view of components of the assembly in FIG. 11, shownin cross section in an unlocked arrangement;

FIG. 19 is a truncated perspective view of components of the assembly inFIG. 11; and

FIG. 20 is a truncated side view of the assembly in FIG. 11.

DETAILED DESCRIPTION OF EMBODIMENTS

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the embodiments shown. Various modifications may be made inthe details within the scope and range of equivalents of the claims andwithout departing from the invention.

Assemblies in accordance with the invention may include an adjustablearticulating assembly for implantation in a human or animal. Theadjustable articulation assembly may include a first elongated elementfor attachment to a first anatomical region, and a second elongatedelement for attachment to a second anatomical region. The assembly mayalso include a coupling connecting the first elongated element with thesecond elongated element. The coupling may include a moveable jointconfigured to allow polyaxial movement of the first elongated elementwith respect to the second elongated element. The coupling may alsoinclude a locking mechanism. The locking mechanism may be operable in anunlocked condition to permit polyaxial movement of the first elongatedelement with respect to the second elongated element. The lockingmechanism may also be operable in a locked condition to immobilize themovable joint and fix the position of the first elongated element withrespect to the second elongated element.

The assembly may include a moveable joint that includes a ball andsocket joint. The ball and socket joint may include a spherical end onat least one of the first elongated element and the second elongatedelement. The first elongated element may be movable through an angle ofat least about 20° relative to the second elongated element.

The locking mechanism may include at least one screw. The screw mayinclude a tapered wedge portion. The screw may directly engage one ofthe first and second elongated elements when the locking mechanism is inthe locked condition.

The moveable joint may feature a hollow receptacle. The hollowreceptacle may be generally spherical. Alternatively, the hollowreceptacle may be generally cylindrical. The hollow receptacle mayinclude at least one open end. The open end may form an enlarged openingthat passes into the hollow receptacle. The enlarged opening may includea tapered edge that tapers outwardly. The hollow receptacle may includeat least one annular seat. The annular seat projects inwardly into asocket in the hollow receptacle.

The at least one annular seat may form a constricted opening having afirst diameter. One of the first and second elongated elements mayinclude a ball end disposed in the hollow receptacle, the ball endhaving a second diameter larger than the first diameter. The ball endmay be compressed against the seat when the locking mechanism is in thelocked condition.

The first and second elongated elements may be associated withassemblies that are implanted in various areas of a human or animal. Forexample, the first and second elongated elements may be associated withrod implants. The first and second elongated elements may includesections of an occipital spine fusion rod. Alternatively, the first andsecond elongated elements may include sections of a lumbar spine fusionrod. This description will now discuss embodiments that feature rods,with the understanding that assemblies in accordance with the inventioncan be used with other elongated elements.

Applicants have developed an articulating fixation assembly that allowsthe rod's angle to be easily adjusted in multiple planes. Angularadjustment is done by moving an articulating joint between the first andsecond sections, as opposed to bending the rod. The articulating jointsimplifies the task of adjusting the rod angle, and creates no stress inthe rod material. By adjusting the rod angle in multiple planes, the rodcan be adjusted to not only match the patient's anatomy, but also meetadditional spatial requirements necessitated by other components of theassembly or instrumentation.

Referring now to FIGS. 2-10, an articulating fixation assembly 200 isshown in accordance with a first exemplary embodiment. Assembly 200includes two rods 210, one of which is shown, and one of which is notshown for clarity. Rod 210 includes a first section 210 a, a secondsection 210 b and a coupling 270 that interconnects the first and secondsections together. First section 210 a, which is truncated for clarity,is secured to a screw assembly 220. Second section 210 b is connected toan occipital plate 260. It will be understood that first section 210 amay be longer and connect with multiple anchors, like hooks oradditional screw assemblies. In addition, it will be understood thatassembly 200 includes two rods 210 that may be configured identically ordifferently.

FIGS. 6-8 illustrate how coupling 270 can be used to adjust theangulation between the first and second sections 210 a and 210 b.Coupling 270 is formed by a ball and socket joint. Specifically,coupling 270 includes a spherical ball end 272 on one end of firstsection 210 a. Coupling 270 further includes a receptacle 274 on one endof the second section 210 b. Receptacle 274 includes a rounded socket276 adapted to receive ball end 272 inside the receptacle. Ball end 272and socket 276 form the ball and socket joint that allows the firstsection 210 a of rod 210 to move polyaxially with respect to the secondsection 210 b. As used herein, the term “polyaxial” or “polyaxially”refers to the ability of a first element to pivot in multiple planeswith respect to a second element to which the first element is coupled.First section 210 a can move polyaxially with respect to second section210 b, and vice versa, so that the two sections can pivot in multipleplanes with respect to one another. In this arrangement, second section210 b can pivot with respect to first section 210 a in ananterior-posterior plane shown by arrows AP in FIG. 6, and amedial-lateral plane shown by arrows ML in FIG. 9.

Receptacle 274 has a generally spherical shape with two flattenedsections 274 a and 274 b. Flattened section 274 a lies adjacent to anenlarged opening 275 that passes through the receptacle 274 and into thesocket 276. Enlarged opening 275 has a tapered edge 275 a and a diameterthat increases as the tapered edge extends outwardly and away from thecenter of receptacle 274. As such, tapered edge 275 a forms afrustoconical surface around enlarged opening 275. Enlarged opening 275and tapered edge 275 a allow first section 210 a to pivot polyaxiallythrough a wide range of motion relative to second section 210 b.

Flattened section 274 b includes a passage 277 and a locking screw 278in the passage. Locking screw 278 includes an external thread thatengages an internal thread in passage 277. As such, locking screw 278 ismovable in passage 277 by threading the screw into the passage andaxially rotating the screw. Passage 277 extends into rounded socket 276.Locking screw 278 is movable in passage 277 between a locked positionand an unlocked position. In the locked position, locking screw 278 ispositioned in passage 277 and extends into rounded socket 276 to engageball end 272. When locking screw 278 engages ball end 272 in the lockedposition, the locking screw compresses the ball end in the socket 276.In this compressed condition, frictional forces between ball end 272,screw 278 and the socket wall 276 immobilize the ball end and prevent itfrom pivoting, so that the first section 210 a of rod 210 is locked inposition relative to second section 210 b. In the unlocked position,locking screw 278 is positioned in passage 277 out of contact with ballend 272, leaving the ball end free to move in socket 276. This allowsfirst section 210 a to pivot polyaxially relative to second section 210b.

FIGS. 11-20 illustrate an articulating fixation assembly 300 shown inaccordance with a second exemplary embodiment. Assembly 300 includes tworods 310, one of which is shown, and one which is not shown for clarity.Rod 310 includes a first section 310 a, a second section 310 b and acoupling 370 that interconnects the first and second sections together.First section 310 a, which is truncated for clarity, is secured to ascrew assembly 320. Second section 310 b is connected to an occipitalplate 360. It will be understood that first section 310 a may be longerand connect with multiple anchors, like hooks or additional screwassemblies. In addition, it will be understood that assembly 300includes two rods 310 that may be configured identically or differently.

FIGS. 15-17 illustrate how coupling 370 can be used to adjust theangulation between the first and second sections 310 a and 310 b.Coupling 370 includes a spherical ball end 372 on one end of firstsection 310 a. Coupling further includes a receptacle 374 on one end ofthe second section 310 b. Receptacle 374 includes a cylindrical socket376 adapted to receive ball end 372 inside the receptacle. Ball end 372and socket 376 form the ball and socket joint that allows the firstsection 310 a of rod 310 to move polyaxially with respect to the secondsection 310 b. First section 310 a and second section 310 b can pivot inmultiple planes with respect to one another. In this arrangement, secondsection 310 b can pivot with respect to first section 310 a in ananterior-posterior plane shown by arrows AP in FIG. 16, and amedial-lateral plane shown by arrows ML in FIG. 19.

Receptacle 374 has a generally cylindrical body 374 b with one open end374 a. Open end 374 a has an enlarged opening 375 that passes throughthe receptacle wall and into the socket 376. Enlarged opening 375 has atapered edge 375 a that tapers outwardly, allowing first section 310 ato pivot polyaxially through a wide range of motion relative to secondsection 310 b. Receptacle 374 further includes an annular seat 379 thatprojects radially inwardly into socket 376 as shown, just inside openend 374 a. Seat 379 forms a constricted opening 379 a having a diameterless than the diameter of ball end 372. In this arrangement, seat 379prevents ball end 372 from exiting socket 376. Ball end 372 restsagainst seat 379 is slidable engagement, while being captively containedin socket 376.

Body 374 b includes a passage 377 that connects with socket 376. Alocking screw 378 is contained in the passage. Locking screw 378includes an external thread that engages an internal thread in passage377. As such, locking screw 378 is movable in passage 377 by threadingthe screw into the passage and axially rotating the screw. Locking screw378 also includes a tapered shaft or wedge portion 378 a that extendsinto socket 376.

Locking screw 378 is movable in passage 377 between a locked positionand an unlocked position. In the locked position, wedge portion 378 a oflocking screw 378 extends into socket 376 and engages ball end 372. Whenlocking screw 378 engages ball end 372 in the locked position, thelocking screw compresses or wedges the ball end against seat 379,trapping the ball end between the wedge portion 378 a and seat. In thistrapped condition, frictional forces between ball end 372 and seat 379,and frictional forces between the ball end and wedge portion 378 a,immobilize the ball end and prevent it from pivoting relative to socket376. As such, first section 310 a of rod 310 is locked in positionrelative to second section 310 b. In the unlocked position, lockingscrew 378 is positioned in passage 377 with wedge portion 378 a out ofcontact with ball end 372. This leaves ball end 372 free to move insocket 376, so that first section 310 a can pivot polyaxially relativeto second section 310 b. FIGS. 15-17 show three different arrangements,each in a locked condition. FIG. 18 shows an arrangement in an unlockedcondition.

The embodiments described thus far provide the benefit of a smootharticulating connection between first and second elongated elements. Theconnection allows multi-planar rotation that permits angular adjustmentof the rod sections not only in the anterior-posterior plane but alsothe medial-lateral direction. Preferably, the connections in eitherembodiment provide about 20° of motion in each allowable direction (40°total through a given plane). A smaller or larger range of motion in oneor more directions may be desirable in certain cases, and are thereforealso contemplated. For example, the connections may permit a maximum ofabout 10° of motion in any allowable direction, or a maximum of about15° of motion in any allowable direction. Or, the connections may permita maximum of about 25° of motion in any allowable direction, or amaximum of about 30° of motion in any allowable direction.

The range of motion for a specific coupling may be controlled by thesize and shape of the openings in the receptacles, through which the rodsections extend. For example, the size and shape of opening 375 may becustomized to permit different ranges of motion in different planes.Where it is desired to have a larger range of motion in one plane, and asmaller range of motion in another plane, the opening through which therod section extends may be elliptical in shape, with the major axis (orwidest dimension) of the elliptical opening aligned with the plane toreceive the largest range of motion. Various openings having symmetricaland asymmetrical shapes may be used to control the range of pivot motionof the rod sections.

The embodiments that have been described thus far provide examples ofarticulating assemblies that permit angulation of rod sections inmultiple planes. The foregoing examples do not represent the onlypossible arrangements that are contemplated. The features of oneembodiment may be added to or substituted for features in anotherembodiment. Numerous variations, changes and substitutions will occur tothose skilled in the art without departing from the principles describedherein.

For example, an articulating rod assembly may include a receptacle withtwo or more locking elements that are advanced into the socket to lockthe ball end in a locking position. The locking elements may be setscrews with or without tapered wedge portions that engage the ball end.Alternatively, the locking elements can be non-threaded elements, suchas a simple shim which is physically pushed into the socket against theball end to prevent the ball end from pivoting in the socket. Thelocking elements may be removable from the receptacle, or captivelycontained in the wall of the receptacle.

Articulating rod assemblies in accordance with the invention may alsoinclude multiple ball and socket joints within a single coupling. In oneembodiment, the coupling is a cylindrical coupling with a sphericalsocket at each end. Each rod section includes a ball end, like firstelongated element 310 a in FIG. 15. Each ball end is disposed in one ofthe sockets, forming two ball and socket joints positioned at oppositeends of the cylindrical coupling. The ball and socket joints allow bothrod sections to move polyaxially with respect to the cylindricalcoupling, and to one another. A pair of locking mechanisms, such as setscrews, extend through a wall of the cylindrical coupling. Each setscrew is used to lock and unlock one of the ball and socket joints.

The receptacles may have various inner and outer geometries. Moreover,the receptacles may include one or more finger tabs or other externalfeatures that allow a surgeon to easily grip and pivot the coupling. Thebody of the receptacle and rods may include markings or indicia toassist the surgeon in monitoring, measuring or approximating the angularadjustments being made between the rod sections.

While the embodiments presented thus far are described in use withoccipitocervical fixation assemblies, articulating assemblies inaccordance with the invention may be used in a variety of applications.For example, an articulating assembly can be used to interconnect firstand second rod sections that are implanted in the lumbar region of thespine. The first and second rod sections may be arranged in an offsetconfiguration, with the articulating coupling providing the desiredoffset between the rod sections.

Articulation assemblies in accordance with the invention can also beused in a rod to rod connector construct. The articulating assembly canconnect an existing fusion construct with another, to treat scoliosis oradjacent segment disease. A new rod fixation system can be connected toan existing rod using the articulating assembly.

Articulating assemblies in accordance with the invention may also beused in a variety of applications outside of spine surgery, includingany applications where elongated members are connected to one another,or to other structures. It should be understood that assemblies inaccordance with the invention need not be used with rods, as notedabove. Assemblies in accordance with the invention may feature elongatedelements in the form of elongated plates, shafts, or any type ofelongated body member.

All such variations are contemplated as part of this disclosure andcovered by the appended claims.

What is claimed:
 1. An adjustable articulating rod assembly forimplantation in a human or animal, the assembly comprising: a firstelongated element for attachment to a first anatomical region; a secondelongated element for attachment to a second anatomical region; and acoupling connecting the first elongated element with the secondelongated element, the coupling comprising: a moveable joint configuredto allow polyaxial movement of the first elongated element with respectto the second elongated element; and a locking mechanism operable in anunlocked condition to permit polyaxial movement of the first elongatedelement with respect to the second elongated element, and a lockedcondition to immobilize the movable joint and fix the position of thefirst elongated element with respect to the second elongated element. 2.The assembly of claim 1, wherein the moveable joint comprises a ball andsocket joint.
 3. The assembly of claim 2, wherein the ball and socketjoint comprises a spherical end on at least one of the first elongatedelement and the second elongated element.
 4. The assembly of claim 1,wherein the first elongated element is movable through an angle of atleast about 20° relative to the second elongated element.
 5. Theassembly of claim 1 wherein the locking mechanism comprises at least onescrew.
 6. The assembly of claim 5, wherein the at least one screwcomprises a tapered wedge portion.
 7. The assembly of claim 5, whereinthe at least one screw directly engages one of the first and secondelongated elements when the locking mechanism is in the lockedcondition.
 8. The assembly of claim 1, wherein the moveable jointcomprises a hollow receptacle.
 9. The assembly of claim 8, wherein thehollow receptacle is generally spherical.
 10. The assembly of claim 8,wherein the hollow receptacle is generally cylindrical.
 11. The assemblyof claim 8, wherein the hollow receptacle comprises at least one openend.
 12. The assembly of claim 11, wherein the at least one open endforms an enlarged opening that passes into the hollow receptacle. 13.The assembly of claim 12, wherein the enlarged opening comprises atapered edge that tapers outwardly.
 14. The assembly of claim 8, whereinthe hollow receptacle comprises at least one annular seat.
 15. Theassembly of claim 14, wherein the at least one annular seat projectsinwardly into a socket in the hollow receptacle.
 16. The assembly ofclaim 14, wherein the at least one annular seat forms a constrictedopening having a first diameter.
 17. The assembly of claim 16, whereinone of the first and second elongated elements comprises a ball enddisposed in the hollow receptacle, the ball end having a second diameterlarger than the first diameter.
 18. The assembly of claim 17, whereinthe ball end is compressed against the seat when the locking mechanismis in the locked condition.
 19. The assembly of claim 1, wherein thefirst and second elongated elements comprise sections of a occipitalspine fusion rod.
 20. The assembly of claim 1, wherein the first andsecond elongated elements comprise sections of a lumbar spine fusionrod.